The present invention relates to a method of manufacturing an optical element, notably an optical element for creating a retractable sheet for use in a motor vehicle. The present invention also relates to an optical element, notably an optical element for creating a retractable sheet for use in a motor vehicle, and also to a display device, notably for motor vehicles.
Display devices using the head-up display principle have been in routine use in the field of motor vehicles for a few years now.
Head-up display devices allow information to be projected into the field of view when looking at the space in front of the motor vehicle so that the driver of the motor vehicle can read this information without taking his eyes off the space in front of the motor vehicle. At the same time, the driver of the motor vehicle can read the information without his eyes having to accommodate.
Certain display devices use the windshield in order to project the information into the field of view when looking at the space in front of the motor vehicle. Although such a device might in theory appear to be advantageous, particularly as regards the number of components needed, the inclination of the windshield or of any other window in a motor vehicle meets aerodynamic criteria or criteria concerned with the mechanical strength/stability of the motor vehicle and thus does not always offer an angle of inclination that is advantageous for the positioning of the display in the field of view of the driver of the motor vehicle. For this reason, certain motor vehicles have been fitted with head-up display devices that comprise an independent reflective sheet.
In order to be used in such a way, an optical element, acting as a retractable sheet in a motor vehicle display device, needs to have optical properties which are such that the optical element is at least partially reflective and/or at least partially transparent. Such optical properties can be achieved using functional coatings, notably reflective or non-reflective coatings (which allow or increase the transmission of light through the optical element).
An optical element according to the present invention may also be referred to as a disk or a sheet or even a combiner because it superposes (or combines) optical information about the field of view of the space in front of the motor vehicle with information from the display device.
Such an optical element is normally manufactured using a three-dimensional forming process, notably a thermoforming process, for example injection molding. Such methods of manufacturing a three-dimensional optical element are generally known.
One disadvantage with such a method is that, in the prior art, the methods of manufacturing optical elements normally intend a step of milling at least one edge surface of the optical element. Such a step of modifying the surface of the optical element, notably the edge surface of the optical element, represents a considerable proportion of the costs of manufacturing the optical element.